Objectives Core B plays the role of a Data Coordinating Center in a multi-component research project. As such, Core B has been designed to provide support to Projects I-V in three broadly defined areas - Data Collection, Data Management, and Data Analysis. The specific objectives of Core B are to (a) facilitate data collection of project specific data for Projects I-V, (b) develop tools and procedures for ensuring and monitoring the accuracy and confidentiality of all collected data, (c) develop tools and procedures to aid the Principal Investigator in providing scientific oversight and administration of the LD Center project, (d) facilitate communication and sharing of data among investigators through state of the art computer networking, and (e) provide statistical support and analyses to investigators in the evaluation of the Project hypotheses.